Railway car draft gfar with automatic cushioning control



L 0 R T N O C G N I N 0 I H s w N m T m m 5T U A. A LH G H .W HR A E WGT F A R D R m 7 6 9 W1 n, 6 M2 8 l u J d e l i F Feb 25, 1969 Sheet I 23M mm 9 om m3 h 5 RIDIGUM INVENTOR. WILLIAM H GLASS BYROBERTJB aATTORNEY N Ki \w Feb. 25, 1969 w, L S ET AL 3,42%,454

RAILWAY CAR DRAFT GEAR WITH AUTOMATIC CUSHIONING CONTROL Filed July 26,1967 Sheet 2 of 2 INVENTOR. WILLIAM HGLASS BY ROBETJ. BRIDIGUM ATTORNEYUnited States Patent O 3,429,454 RAILWAY CAR DRAFT GEAR WITH AUTOMATICCUSHIONING CONTROL William H. Glass and Robert J. Bridigum, Pittsburgh,Pa., assignors to Westinghouse Air Brake Company, Wilmerding, Pa., acorporation of Pennsylvania Filed July 26, 1967, Ser. No. 656,187 US.Cl. 213-8 14 Claims Int. Cl. B61g 9/12, 11/00, 9/02 ABSTRACT OF THEDISCLOSURE A don-bled piston hydraulic draft gear device for a cashionednnderframe type of railway car having a body supporting sliding orfloating center still straddling a fixed center sill and movablerelative thereto in response to inettia forces effective on the car bodyto cause one piston to act jointly with car coupler bufiing forceseffective on the other piston to provide for energy absorptionproportional to the load on the car and effective to act in oppositionto the downward pitching of the front end of the car resulting from theimpacting of the car with another upon coupling of the couplers of therespective cars.

Conventional cushioned underframe type of railway cars comprise a singlepiston and cylinder device subject to both the inertia forces resultingfrom the movement of the body-supporting sliding sill relative to thefixed center sill occurring upon impacting of a moving car with astationary car and the bufling force imparted to the car couplers uponthe moving car striking the stationary car. Since this single cylinderdevice must be capable of providing for the absorption of both inertiaand buff forces, the length of stroke of this device and thecorresponding amount of movement of the sliding sill with respect to thecenter sill is unduly long thereby resulting in a reduction in thelength of the car body relative to the distance between coupler faces atthe respective opposite ends of the car.

Accordingly, it is the general purpose of this invention to provide anautomatic load-controlled hydraulic draft gear embodying twoparallel-related integral hydraulic cylinder devices, subjectrespectively to inertia forces resulting from movement of abody-supporting sliding sill and bufiing forces active on a car coupler,thereby enabling an increase in the length of the car body relative tothe distance between coupler faces without a reduction in energyabsorption by the draft gear which is adapted to fit within the yokepocket of a draft gear yoke.

More specifically, according to the invention, two parallel integralhydraulic cylinder devices each having a piston subject respectively toinertia forces and butting forces, in response to which said pistonscause a fluid displacement from the corresponding cylinder to a loadsensing and weighing cylinder device interposed bebween a car bolsterand a car body to cause a correspondingly upward displacement of apiston within the cylinder device whereby the weight of the car body andload carried thereon is used to resist the upward movement of thispiston. Furthermore, this upward movement imparted to the car body bythis piston is effective to counteract the rocking of the car body aboutits center of gravity as a result of the decelerated forces acting onthe car. Accordingly, this multipiston and cylinder arrangement providesautomatic car cushioning control in accordance with the load carried bythe car.

In the accompanying drawings:

FIG. 1 is an elevational cross-sectional view of a novel hydraulic draftgear device for a railway freight car.

Patented Feb. 25, 1969 FIG. 2 is an elevational cross-section view,taken along the line 22 of FIG. 1 and looking in the direction of thearrows, showing the construction and arrangement of a car bolster onwhich is mounted a load-weighing cylinder device that respectivelysupports a fixed center s'ill and a body-supporting sliding center sill.

FIG. 3 is an elevational cross-sectional view, taken along the line 33of FIG. 1 and looking in the direction of the arrows, showing how thedraft gear device is disposed between the opposite sides of a horizontaltype of draft gear yoke and within the fixed center sill.

In FIGS. 1, 2 and 3 of the drawings is shown a cushioned draft geardevice constructed in accordance with the invention. This draft geardevice is carried in an elongated yoke pocket or slot 1 formed betweenparallel and spacedapart left and right-hand vertical walls 2 (FIGS. 2and 3) and 3 of a draft gear yoke 4. The left-hand end of the draft gearyoke 4 is provided, as shown in FIG. 1, with a substantially rectangularshaped opening 5 in which is received a shank 6 of a railway freight carcoupler, the head of which has been omitted from the drawings since itforms no part of the invention. The right-hand end of the shank 6 abutsthe left-hand vertical face of a follower 7 that is disposed within theyoke pocket 1, it being understood that the width of this follower isthe same as the width of the yoke pocket 1 and that this follower isplaced in this yoke pocket subsequent to placing the draft gear devicetherein.

The shank 6 is provided with an elongated slot 8 for receiving a shankpin 9 that extends through corresponding coaxial elongated slots (notshown) in the opposite vertical side walls 2 and 3 of the draft gearyoke 4 and also through a pair of aligned substantially rectangularholes or slots 10 formed respectively in a pair of spaced-apart verticalparallel walls adjacent the left-hand end of a fixed center sill 11, itbeing apparent from FIG. 1 that the length of these slots 10 issubstantially greater than the length of the slot 8 in the shank 6. Theshank pin 9 is retained in place by a cotter pin (not shown). The shankpin 9 thus provides an operative connection between shank 6 of the carcoupler and the draft gear yoke 4 through which draft forces aretransmitted to the draft gear device. Buff forces are transmitteddirectly from the shank 6 of the car coupler to the draft gear device ina manner hereinafter made apparent.

After the shank 6 of the car coupler has been secured to the draft gearyoke 4 by the shank pin 9, a hollow boxlike striker 12, having extendingtherethrough a rectangular-shaped opening that is somewhat larger incross-section than the cross-section of the draft gear yoke 4, isslipped over the right-hand end of the draft gear yoke 4 and moved inthe direction of the left-hand, as viewed in FIG. 1, until the left-handend of the striker 12 is substantially in alignment with the left-handend of the draft gear yoke 4. The striker 12 is allowed to rest in thisposition on the draft gear yoke 4 until a draft gear device 13hereinafter described is assembled and then placed in the yoke pocket 1.

As can be seen from FIGS. 2 and 3 of the drawings, thehereinbefore-mentioned fixed center sill 11 may be fabricated as bywelding 21 top plate 14 to two oppositely arranged American Associationof Railroads Z-sections 15 and 16 so as to form a fixed center sillpocket 17. Thereafter, an elongated slot 18 (FIG. 1) is formed, as by,for example, the use of an acetylene torch, in the top plate 14 and theupper flanges of the Z-sections, 15 and 16 (FIG. 2), the purpose of thisslot 18 being to accommodate the upper portion of the draft gear device13 which extends therethrough and also through an elongated slot 19(FIG. 1) formed in a floor 20 of the railway car adjacent the left-handend thereof, this end of the fioor being supported by an end sill (notshown) as is conventional in railway freight car construction.

The floor 20 to the right of the draft gear device 13, as shown in FIG.1, is supported by a sliding or floating center sill 21, it beingunderstood that the entire car body is supported by and movable withthis center sill in response to draft and buff forces imparted to thecar coupler.

As shown in FIG. 2, the sliding sill 21 may be fabricated as by Weldinga top plate 22 to two oppositely arranged American Association ofRailroads Z-sections 23 and 24 which are arranged in straddling relationto the fixed center sill 11 so as to form between the fixed center sill11 and the sliding sill 21 a sliding sill pocket 25. Subsequent to thiswelding operation, the main underframe is secured to the sliding sillupon which underframe, it will be understood, the car body including thehereinbefore-mentioned floor 20 is constructed according to conventionalpractice of railway car builders.

The draft gear device 13 comprises a single casing 26 (FIG. 1) in whichis embodied two parallel hydraulic cylinder devices or fluid motors 27and 27a. The single casing 26 is provided with two spaced-apart paralleland oppositely extending bottom bores 28 and 29, the bottom bore 28being arranged vertically above the bottom bore 29 and opening in theopposite direction. As shown in FIG. 1, the left-hand end of the upperbottom bore 28 is connected to the right-hand end of the lower bottombore 29 by a passageway 30 formed in the casing 26.

As can be seen from FIG. 1, the casing 26 has formed therein a chamber31 which is in communication with the passageway 30 via a tapered bore32 provided in the casing 26.

As shown in FIG. 1 of the drawings, a piston 33 is provided with aperipheral annular groove in which is inserted an O-ring 34 prior toplacing the piston 33 in the bottom bore 28. Also, prior to placing thepiston 33 in the bottom bore 28, the left-hand end of a piston rod 35 ispress-fitted into a bottom bore 36 provided in the righthand face ofthis piston.

Subsequent to securing the piston rod 35 to the piston 33 and insertingthe O-ring 34 in the groove in this piston in the manner just explained,the piston 33 is introduced into the right-hand end of the bottom bore28 in the easing 26.

Next, a nonpressure head 37 having a central bore 38 is slipped over theright-hand end of the piston rod 35 and then pushed in the direction ofthe left-hand, as viewed in FIG. 1, until it is in abutting relationshipwith the right-hand end of the cylinder device 27. The pressure head 37is then secured to the right-hand end of this cylinder device 27 by anysuitable means (not shown).

As can be seen from FIG. 1, the pressure head 37 is provided with acounterbore 39 coaxial with the bore 38. A packing 40 is first placed inthis counterbore 39 after which an annular packing nut 41 is slippedover the righthand end of the piston rod 35 and then screw threaded intoa screw-threaded counterbore 42 that is coaxial with the counterbore 39.The packing nut 41 thus serves to retain the packing 40 in thecounterbore 39 and in sealing relationship with the periphery of thepiston rod 35.

The hydraulic cylinder device 27a of the draft gear device 13 comprisesa piston 43 that is provided with a peripheral annular groove, a centralbore 44 and a coaxial screw-threaded counterbore 45.

Prior to placing the piston 43 in the bottom bore 29, an O-ring 46 isinserted in the peripheral annular groove in this piston. Also, a pistonrod 47 having external screw threads corresponding to the internal screwthreads of counterbore 45 is screw threaded into this counterborethereby securing this piston rod 47 to the piston 43.

Formed integral with the threaded end of the piston rod 47 is a taperedmetering pin or plunger 48 that extends through the bore 44 in thepiston 43. The taper per inch of the metering pin 48 is the Same as thatof the tapered bore 32. However, it should be noted that the diameter ofthe metering pin 48 at its larger or left-hand end is somewhat less thanthe diameter of the tapered bore 32 at its left-hand end.

Subsequent to inserting the O-ring 46 in the groove in the piston 43 andsecuring the piston rod 47 thereto, this piston is positioned so thatthe metering pin 48 extends in the direction of the bottom bore 29 inthe casing 26 and is coaxial with this bottom bore. With the piston 43and metering pin 48 thus positioned, they are moved toward the casing 26and the piston 43 introduced into the left-hand end of the bottom bore29 in this casing 26.

Next, a nonpressure head 49 having a central bore 50 is slipped over theleft-hand end of the piston rod 47 and then pushed in the direction ofthe right-hand, as viewed in FIG. 1, until it abuts the left-hand end ofthe cylinder device 27a. This pressure head 49 is then secured to theleft-hand end of the cylinder device 27a by any suitable means (notshown).

As shown in FIG. 1, the pressure head 49 is provided with a counterbore51 that is coaxial with the bore 50 and has internal screw threadsformed adjacent its outer end. A packing 52 is now placed in thecounterbore 51 after which an annular packing nut 53 is slipped over theleft-hand end of the piston rod 47 and thereafter screw threaded intothe screw-threaded end of the counterbore 51 to retain the packing 52therein.

Subsequent to assembling the draft gear device 13 in the manner justexplained, the pistons 33 and 43 are respectively moved from theposition in which they are shown in FIG. 1 to a position at the oppositeend of the corresponding bottom bores 28 and 29 by manually exerting apush on the outer end of the respective piston rods 35 and 47.

Assuming that the fixed center sill 11 is positioned within the slidingsill pocket 25 of the Sliding Sill 21 in the position indicated in FIG.2, and further assuming that the car body-supporting sliding sill 21 andthe fixed center sill 11 are supported by any suitable means, such as,for example, the usual overhead crane found in railway car buildersassembly plants, the hereinbefore-mentioned assembly including the draftgear yoke 4, to which is secured the car coupler by having its shank 6secured thereto by the shank pin 9, and the striker 12, which is restingon the left-hand end of the draft gear yoke 4, is positioned below thefixed center sill pocket 17 so that the center line of this assembly isparallel with the center line of the center sill pocket 17 and the fixedcenter sill 11.

The above-described assembly may now be raised vertically by anysuitable means (not shown) until it is positioned within the fixedcenter sill pocket 17 as shown in the drawings. This assembly is nowretained temporarily in this position by any suitable means (not shown).

The horizontal type of draft gear yoke 4 is permanently supported by twoparallel spaced-apart longitudinally extending angle brackets 54 and 55(FIGS. 2 and 3) which are now secured by any suitable means, such as forexample, welding or a plurality of rivets, respectively to the insidevertical faces of the hereinbefore-mentioned Z-sections 15 and 16. Itwill be understood that subsequent to securing these angle brackets 54and 55 to the respective Z-seotions 15 and 16, thehereinbefore-mentioned means for temporarily retaining the assemblyincluding the draft gear yoke 4 in the position shown in the drawings isnow removed.

Next, the assembled draft gear device 13 is positioned below the draftgear yoke 4 so that the center lines of the piston rods 35 and 47 areparallel :to the horizontal center line of the yoke 4. The draft geardevice 13 may now be moved upward by any suitable means (not shown), sothat the upper portion of the casing 26 of this draft gear device passesthrough the yoke pocket 1 in the draft gear yoke 4, the elongated slot18 in the fixed center sill 11, and the elongated slot 19 in the Carfloor 20, until this draft gear device 13 occupies the position shown inthe drawings.

At this time a draft gear carrier plate 56 is secured by any suitablemeans, such as, for example spot welding, to feet 57 and 58 (FIGS. 2 and3) that are integral with the respective Z-sections 15 and 16 of thefixed center sill 11. The width of this draft gear carrier plate 56, asshown in FIG. 2, is substantially greater than the width of the fixedcenter sill 11 or the distance between the opposite ends of the feet 57and 58 in order to support thereon adjacent each of these feet aplurality of rollers 59 which are disposed between this carrier plate 56and feet 60 and 61 that are integral with the respective Z-sections 23and 24 of the sliding sill 21. These rollers 59 are retained on the topsurface of the carrier plate 56 between the feet 57 and 58 of therespective Z-sections 15 and 16 and a pair of vertically disposed skirts62 and 63 which are secured respectively to the feet 60 and 61 by anysuitable means, such as, for example, spot welding along their upperedge. It will be apparent from FIG. 2 that the skirts 62 and 63 and thefeet 57 and 58 provided a track for the plurality of rollers 59 whichroll therealong and support the car body-carrying sliding sill 21 uponmovement thereof in response to draft and buff forces in a mannerhereinafter described in detail.

Furthermore, it will be apparent from the drawings that, subsequent tosecuring the draft gear carrier plate 56 to the feet 57 and 58 of therespective Z-sections 15 and 16 of the fixed center sill 11, thiscarrier plate supports thereon the casing 26 of the draft gear device13. Therefore, the means used to move this draft gear device 13 upwardto the position shown in the drawings and maintain it in this positionuntil the carrier plate 56 is secured to the feet 57 and 58, may now beremoved.

Subsequent to positioning the draft gear device 13 in the position inwhich it is shown in FIG. 1, the pistons 33 and 43 are moved to theposition shown in FIG. 1 by manually exerting a pull on the respectivepiston rod 35 and 47. With the pistons 33 and 43 and the piston rods 35and 47 in this position, the right-hand end of the piston rod 35 abuts abumper block 64 which is disposed in an opening 65 formed in the carfloor 20 and secured, as for example by welding, to the top plate 22 ofthe sliding sill 21 so as to be movable therewith.

It will be noted from FIG. 1 that, while the piston 43 and piston rod 47occupy the position shown, the left-hand end of the piston rod 47 abutsthe right-hand vertical face of the hereinbefore-mentioned follower 7.

The left-hand vertical face of the follower 7, in addition to abuttingthe right-hand end of the shank 6 of the car coupler, ashereinbefore-stated, also abuts a pair of front draft gear lugs 66 and67 which are secured respectively, as for example, by welding, to thetop flanges of the two Z-sections 15 and 16 constituting the fixedcenter sill 11, and to the draft gear carrier plate 56, it beingunderstood this welding operation is performed prior to welding theplate 56 to the feet 57 and 58 of the Z-sections 15 and 16. These frontdraft gear lugs 66 and 67 serve to transmit draft forces to the fixedcenter sill 11, it being understood that these forces are transmittedthrough the draft gear device 13.

In order that buff forces imparted to the draft gear device 13 via thecar coupler during humping operations may be transmitted to the fixedcenter sill 11, a pair of rear draft gear lugs 68 and 69 are securedrespectively, as for example by welding, to the top flanges of the twoZ- sections 15 and 16, and to the carrier plate 56 as shown in FIG. 1,it being understood that this welding operation is also performed priorto welding the draft gear carrier plate 56 to the feet 57 and 58.

In place of a conventional truck bolster, each car truck of a freightcar equipped with two draft gear devices 13 constituting the presentinvention, one located adjacent each end of the car, is provided with aspecially designed car bolster 70 (FIGS. 1 and 2). Substantially midwayits ends, the car bolster is provided with a vertically disposed bottombore 71 in which is carried a load sensing or weighing cylinder device72.

The load sensing or weighing cylinder device 72, as shown in FIG. 1,comprises a cup-shaped cylinder body 73 having therein a bottom bore 74.Slidably mounted in the bottom bore 74 is a piston 75 which cooperateswith the wall surface and end of the bottom bore 74 to form on the lowerside of this piston 75 a chamber 76.

Extending through the wall of the bottom bore 74 in the cylinder body 73and the wall of the bottom bore 71 in the car bolster 70 is ascrew-threaded bore 77 in which is received a screw-threaded end of ashort nipple 78. The opposite end of this nipple 78 extends into one endof a piece of flexible hose 79 the opposite end of which extends throughan opening 80 suitably formed in the draft gear carrier plate 56 andreceives therein one end of a second short nipple 81. The opposite endof this nipple 81 is provided with external screw threads which havescrew-threaded engagement with corresponding internal screw threadsformed in a bore 82 extending through the casing 26 of the draft geardevice 13 and opening into the chamber 31 in this casing 26. Thus thechambers 76 and 31 are constantly in communication one with the other.

It will be noted from FIG. 1 of the drawings that the upper face of thepiston 75 is provided with a bottom bore 83 into which is press-fittedone end of a hollow piston rod 84. The opposite end of the piston rod 84extends through a bore 85 formed in a non-pressure head 86 that issecured to the upper end of the cylinder body 73 by any suitable means(not shown).

The non-pressure head 86 is provided with a counterbore 87 that iscoaxial with the bore 85. Disposed in this counterbore 87 is a swab orpacking 88 that is saturated with any suitable lubricant for lubricatingthe periphery of the piston rod 84 upon upward movement of the piston 75in the bottom bore 74. The outer end of the counterbore 87 is providedwith internal screw threads for receiving therein corresponding externalscrew threads formed on an annular nut 89 which serves to retain theswab 88 in this counterbore 87.

The upper end of the hollow piston rod 84 is provided with a counterbore90 for receiving therein with a turning fit an annular member 91 that issecured to the bottom of the draft gear carrier 56 by any suitable meanssuch as, for example, welding.

Disposed within the annular member 91 and secured thereto and to thebottom of the draft gear carrier plate 56 by any suitable means (notshown) is a king pin 92 the lower end of which extends with a turningfit through a bore 93 formed in a second annular member 94 that isdisposed in the upper end of the hollow piston rod 84 and securedthereto by any suitable means such as, for example welding. Theabove-described construction provides for turning of the car truck withrespect to the car body which turning is necessary when a railway cartravels on a curved track.

In order to prevent leakage of fluid under pressure from the chamber 76to an annular chamber 95 above the piston 75, this piston is providedwith a peripheral annular groove in which is inserted an O-ring 96 thatforms a seal with the wall surface of the bottom bore 74.

The annular chamber 95 is constantly open to atmosphere via a passageway97 that extends through the cylinder body 73 'and the bolster 70 toprevent dash pot action within the annular chamber 95.

After the draft gear device 13 and the load sensing or weighing cylinderdevice 72 have been assembled and connected by the flexible hose 79 asshown in FIG. 1 of the drawings, and while the car is empty, ascrew-threaded filler plug (not shown) is removed from a correspondingscrew-threaded bore (not shown) in the casing 26. Subsequent to removalof this filler plug, a hydraulic fluid, such as a suitable oil, ispoured into the interior of the casing 26 until the chamber 76, hose 79,chamber 31,

7 tapered bore 32, bottom bore 29 on the right-hand side of piston 43,passageway 30 and the bottom bore 28 on the left-hand side of piston 33are completely filled, after which the filler plug is replaced.

The hereinbefore-mentioned striker 12 may now be moved from the positionin which it was placed, adjacent the left-hand end of the yoke 4, in thedirection of the right-hand, as viewed in FIG. 1, along the yoke 4 untilthe right-hand end thereof can be inserted into the lefthand end of thefixed center sill pocket 17 (FIG. 1), after which the striker 12 ispushed in the direction of the right-hand until it occupies the positionshown in FIG. 1. With the striker 12 in this position, it is welded tothe left-hand end of the fixed center sill 11, as indicated by thereference numeral 98 in FIG. 1.

OPERATION It should be noted that the kinetic energy absorbed by thedraft gear device 13 of the present invention in buff is twice that indraft for the reason that in buff the piston 43 of the hydrauliccylinder device 27a is subjected to the buffing force and the piston 33of the hydraulic cylinder device 27 is subject to the inertia force ofthe car body and the load carried thereby as the result of the movementof the body-supporting sliding sill 21 relative to the fixed center sill11 occurring upon the application of a buffing force to the car couplerwhereas, upon the application of a force of draft to the car coupler,only the piston 43 is subject to this force.

However, it should be noted that upon the application of 4 a force ofdraft to the car coupler at one end of the car, the piston 33 of thedraft gear device 13 at the opposite end of the car is subject to theinertia force of the car body and its load as the result of the movementof the sliding sill 21 relative to the fixed center sill 11 it beingunderstood that the direction of movement of the sliding sill 21 at thistime is opposite the direction of movement of the sliding sill inresponse to the application of a buffing force to the car coupler at theone end of the car.

It will be further noted that the draft gear device 13 at theabove-mentioned opposite end of the car, in addition to being subject tothe inerita force of the car body and its load as the result of themovement of the sliding sill 21 relative to the fixed center sill 11, isalso subject to a draft force resulting from this car being coupled tothe adjacent car. Accordingly, it will be understood that the capacityof each draft gear device 13 is the same in draft as in buff. Therefore,when a car coupled in a train is started from rest by the tractiveeffort of the locomotive, the cylinder device 27a of the draft geardevice 13 on that end of the car nearest the locomotive is subject to adraft force whereas the cylinder device 27 of this draft gear device 13is subjected to no force, and simultaneously the cylinder devices 27aand 27 of the draft gear device 13 on the opposite end of this car aresubject respectively to a draft force and an inertia force.

So long as the kinetic energy developed as the result of a buff or adraft impact imparted by each to the other of two adjacent railway carcouplers upon the colliding of the two cars carrying these couplers doesnot exceed the capacity or amount of kinetic energy for which the draftgear was designed to absorb by more than a certain amount, the stressinduced in the couplers and the various parts constituting the bodies ofthe cars will be limited to a value below or not in excess of theelastic limit of the materials of which the car couplers and car bodiesare constructed.

It should be understood that, in draft, kinetic energy is transmittedfrom the car coupler through the shank pin, the draft gear yoke, thedraft gear device, the follower and the front draft gear lugs to thefixed center sill, and in buff, kinetic energy is transmitted from thecar coupler through the coupler shank, the follower, the draft geardevice and the rear draft gear lugs to the fixed center sill.

(a) Bufj impact-car detached for humping Let it be supposed that adetached freight car, while traveling along a track in a classificationyard at some slow speed such as, for example, fourteen miles per hour,collides with a standing car or string of cars on this track. Thismoving car has a certain amount of kinetic energy. As the couplers onthe adjacent ends of the moving car and the standing car come intocontact, each coupler imparts an impact to the other, the impactimparted to each coupler by the other being the same. These couplersoperate automatically at this time to couple the two cars together.

Let it be assumed that the shank 6 shown in FIG. 1 of the drawings isthe shank of the car coupler on a standing car that is struck by themoving car. Therefore, upon collision of the moving car with thestanding car, some of the kinetic energy of the moving car istransmitted from the coupler on the moving car through the shank 6 ofthe coupler on the struck car and the follower 7 on this car to thecorresponding piston rod 47, it being understood that the direction ofthe blow imparted as the result of this impact acts in the direction ofthe right-hand, as viewed in FIG. 1.

Since the piston rod 47 having metering rod 48 integral therewith hasscrew-threaded engagement with the screwthreaded counterbore 45 in thepiston 43, it is apparent that the piston rod 47 transmits the bufiingforce of impact of the two colliding cars to the piston 43 of the draftgear device 13 on that end of the struck car adjacent the moving car tocause movement of this piston 43 and metering rod 48 in the direction ofthe right-hand relative to the casing 26, the right-hand end of whichabuts the rear draft gear lugs 68 and 69.

This movement of the piston 43 in the direction of the right-hand withinthe bottom bore 29 in casing 26 is in the direction to cause this piston43 to decrease the volume of the bottom bore 29. As the piston 43 andmetering rod 48 are thus moved in the direction of the right hand, thepiston 43 is effective to force the oil in the bottom bore- 29 to flowtherefrom, and the metering rod 48 is moved into the tapered bore 32.

As hereinbefore explained, the bottom bore 28, passageway 30, taperedbore or orifice 32, chamber 31, hose 79 and chamber 76 are all full ofoil. Since the piston 33 is at the righthand end of its stroke, therecan be no flow of oil to the bottom bore 28. Therefore, in order for oilto be forced from the bottom bore 29 by the piston 43, there must be anincrease in the volume of the chamber 76 which can only result fromupward movement of the piston 75 in the bottom bore 74 of the loadweighing cylinder device 72.

As hereinbefore explained, the piston rod 84 of the piston 75 supportsin the counterbore the annular member 91 which is secured to the draftgear carrier plate 56 that in turn supports the rollers 59 on which, asshown in FIG. 2, rest the feet 60 and 61 of the Z-sections 23 and 24 ofthe car-body-supporting sliding center sill 21. Consequently, it isapparent that upward movement of the piston 75 is resisted by one halfthe weight of the car body and the load carried thereon, it beingunderstood that the other half of the weight of the car body and itsload is supported by the identical load weighing cylinder device locatedadjacent the other end of the car.

From the foregoing, it is apparent that the work done by the piston 43in displacing oil from the bottom bore 29 and forcing it into thechamber 76 is equal to the work done by the piston 75 as it lifts theweight of the left-hand end of the car vertically upward a distance thatprovides for an increase in the volume of the chamber 76 that is equalto the volume of the oil forced from the bottom bore 29 by the piston43.

It is well known that the work done in lifting a Weight vertically isequal to the product of the weight and the distance that the weight islifted. Therefore, it is apparent that the greater the load carried onthe car body the 9 greater the weight to be lifted by fluid forced intothe chamber 76 and, therefore, the greater the amount of work done uponupward movement of the piston 75 a chosen distance.

It is apparent that the kinetic energy that is not absorbed in liftingthe weight of the car body and the load carried thereon, or by othermeans hereinafter discussed, is transferred as kinetic energy from thepiston 43- via the oil in the casing 26 to this casing and thence viathe rear draft gear lugs 68 and 69 to the fixed center sill 11 of therespective car with its load .carried in the body thereof which issupported by the sliding sill 21 that in turn is supported on therollors 59 which rest on the draft gear carrier plate 56 that is weldedto the fixed center sill 11. This remaining kinetic energy that is thustransmitted to the standing car is effective to move the standing car,or string of standing cars if one or more cars are coupled to the struckcar, provided this remaining kinetic energy is great enough to overcomethe inertia of the standing car or cars.

Let it be assumed that this remaining kinetic energy is great enough tomove the standing car or string of cars from a standing position. It iswell known that a body or weight possesses that characteristic calledinertia which is defined by Chambers Technical Dictionary, edited by C.F. Tweney and L. E. C. Hughes, revised edition with supplement,published 1961, as follows:

Inertia (Mech., Phys). Reluctance of a body to change its state of restor of uniform velocity in a straight line. Inertia is measured by masswhen linear velocities and accelerations are considered; and by momentof inertia (q.v.) for angular motions (i.e. rotations about an axis).

Accordingly, the car body and the load carried thereon, both of whichare supported on the rollers 59', by reason of their inertia will,therefore, be reluctant to change their state of rest or, in otherwords, resist movement from their state of rest as the result of thekinetic energy transmitted to the corresponding coupler of a standingcar and thence to the fixed center sill 11 of this car. Consequently,this kinetic energy transmitted to the fixed center sill 11 will causemovement of this fixed center sill and the car trucks relative to thesliding center sill 21 upon which is supported the car body and the loadcarried thereon.

Upon this movement of the fixed center sill 11 and casing 26 of thedraft gear device 13 relative to the sliding center sill 21 and the carbody supported thereon, the sliding sill 21 is effective via the bumperblock 64 and piston rod 35 to maintain the piston 33 of the cylinderdevice 27 against movement. Consequently, the casing 26 of the draftgear device 13 now moves in the direction of the right-hand, as viewedin FIG. 1.

It is apparent that, in order for the casing 26 to move in the directionof the right-hand, as viewed in FIG. 1, relative to the stationarypiston 33, the piston 33 forces oil from the bottom bore 28. Since thepiston 43' is subject to the force of the impact of the two collidingcars, as hereinbefore explained, there can be no flow of oil to thebottom bore 29. Accordingly, in order for oil to be forced from thebottom bore 28 by the piston 33 as the casing 26 is moved in thedirection of the right-hand, as viewed in FIG. 1, there must be anincrease in the volume of the chamber 76 and an upward movement of thepiston 75 in the bottom bore 74 against the resistance offered by onehalf the weight of the car body and the load carrier thereon. Therefore,it is apparent that as the load carried by the car is increased, thisresistance is correspondingly increased thus providing for control ofthe resistance to the bufiing forces automatically.

As hereinbefore explained in connection with the displacement of oilfrom the bottom bore 29 to the chamber 76 by the piston 43, it will beapparent that the work done by the piston 33 in displacing oil from thebottom bore 28 and forcing it into the chamber 76 is equal to the 10Work done by the piston 75 as it lifts the weight of the left-hand endof the car upward a distance that provides for an increase in the volumeof the chamber 76 that is equal to the volume of the oil forced from thebottom bore 28 by this piston 33.

It is apparent from FIG. 1 that the oil flow initiated by movement ofboth the piston 33 and the piston 43' from the respective bottom bores28 and 29 to the chamber 31 in the draft gear device 13 and the chamber76 in the load weighing cylinder device 72 is through an orifice formedbetween the periphery of the tapered metering pin 48 and the inside Wallsurface of the tapered bore 32. It is also apparent from FIG. 1 that asthe piston 43 and tapered metering pin 48 move in the direction of theright-hand so that the metering pin 48 travels further into the taperedbore 32, the cross-sectional area of this orifice is decreased.

The oil flow through the orifice provided between the periphery of themetering pin 48 and the Wall surface of the tapered bore 32 is at arelatively high velocity and creates great turbulence in the chamber 31.This great turbulence is caused, at least in part, by the high velocityoil impinging directly against the right-hand vertical wall surface ofthe chamber 31, and is responsible for dissipation of much of thekinetic energy of the oil in the form of heat.

Furthermore, the friction of the draft gear yoke 4 and other movingparts is effective to dissipate or absorb some of this kinetic energy.Therefore, all the kinetic energy transmitted to the car couplers andshank 6 on each of the two colliding cars is dissipated (1) in the formof the work done by the pistons 33 and 43 in forcing oil from therespective bottom bores 28 and 29 to the chamber 76, which is equal tothe work done by the piston 75 in lifting one half the Weight of the carbody and the load carried thereon as this piston 75 is moved upward toincrease the volume of the chamber 76 an amount equal to the volume ofthe oil forced out of the bottom bores 28 and 29 by the respectivepistons 33 and 43, (2) in the form of heat by the passing of the oilthrough the orifice, (3) the turbulence in the chamber 31, and (4) thefriction of the various parts of the draft gear devices, or istransferred via the rear draft gear lugs 68 and 69 to the fixed centersill 11 of the respective car.

The standard coupler used on freight cars is designed to withstand apredetermined buff or compression impact blow Without inducing a stresstherein that exceeds the elastic limit of the steel, of which thecoupler is constructed. In order that the buff stress established by theimpact of the two colliding cars is maintained constant during the timerequired for the pistons 43 and 33 to successively travel their maximumlength of stroke in the respective bottom bores 29 and 28 in the casing26 of the draft gear device 13, the area of the orifice provided by thetapered bore 32 and the metering rod 48 must be varied so as to provideor maintain a constant oil pressure in the bottom bores 29 and 28, whichconstant pressure establishes a corresponding constant force that mustnot exceed the allowable force that can be transmitted through thecasing 26 of the hydraulic gear device 13 to the rear draft gear lugs 68and 69 and thence to the fixed center sill 11 and the car body slidablysupported thereon 'by the sliding sill 21 without inflicting damage tothe lading carried by the car.

As the piston 43 moves in the direction of the righthand in the bottombore 29 of the casing 13 of the hydraulic draft gear device 13 from theposition in which it is shown in FIG. 1 at an initial velocitycorresponding to the degree of the impact blow on the car coupler as theresult of the collison of the moving car with the standing car or cars,the pressure of the oil in the bottom bore 29 is increased at a rapidrate due to the combined effect of the inertia of the oil in thischamber and the limited area of the orifice provided by the tapered bore32 and metering rod 48, through which orifice the oil flows from thebot- 1 1 tom bore 29 to the chamber 31 and thence to the chamber 76 viathe hose 79.

In order that the force developed by the increase of the pressure of theoil in the bottom bore 29 'be limited to and thereafter maintained at avalue which will not induce a stress in either the coupler or thestructure of the car in excess of the elastic limit as the piston 43 andmetering rod 48 move in the direction of the right hand, subsequent tothe right-hand end of the metering rod 48 entering the left-hand end ofthe tapered bore 32, a distance equal to the length of the metering pin48 from its righthand end to the right-hand face of the piston 43, thismetering pin 48 must be tapered this distance, it being understood thatthe taper of the metering pin 48 is the same as that of the tapered bore32, as hereinbefore stated. It will be apparent that as the taperedmetering pin 48 passes through the tapered bore 32, the area of theorifice is decreased at a rate corresponding to the angle of the taperof the metering rod 48. Furthermore, it will be understood that theinitial velocity of the piston 43 has been reduced as it moves in thedirection of the right hand, as viewed in FIG. 1, as part of the kineticenergy of the striking car is absorbed by doing work as each respectiveload weighing cylinder device 72 lifts the corresponding end of therespective car in the manner hereinbefore described. Therefore, in orderto maintain a constant pressure in the bottom bore 29 as the piston 43and meteing pin 48 move in the direction of the right hand with aconstantly decreasing velocity, the area of the orifice provided by thetapered bore 32 and the metering rod 48 must be decreased at a certaincorresponding rate. Consequently, by providing that the metering rod 48is tapered in the direction shown in FIG. 1, this requirement that theorifice area be constantly decreased at this certain constant rate isinsured.

The center of gravity of a railway freight car, whether empty or loaded,is above the horizontal center line of the car couplers. Therefore,normally when a moving car of conventional design strikes a likestanding car or string of cars, a moment is produced on the struck carwhich is the product of the force of impact imparted to this car by themoving car and the vertical distance between the horizontal center lineof the car couplers and the center of gravity of this car. The effect ofthis moment on the struck car is to rotate the body of this struck carabout th center of gravity of the car in the direction to cause that endof the struck car that is adjacent the moving car to clip or movedownward toward the rails, it being understood the car truck springs 'atthis end of the car, which springs resiliently support one half of theweight of the car body and its load it it is loaded, deflect or arecompressed to allow this end of the car to dip downward.

It should be noted, however, that the hereinbeforementioned upwardmovement of the piston 75 in the bottom bore 74 of the load weighingcylinder device 72 acts in the direction to balance or counteract theabove-mentioned moment acting on the car body. Consequently, the dippingthat occurs on cars of conventional design when a moving car strikes astanding car or string of cars is greatly reduced or entirely eliminatedwhen the cars are provided at each end with a draft gear device 13 and aload weighing cylinder device 72 connected by a hose 79 or, in otherwords, when the cars are provided with the apparatus constituting thepresent invention.

Since, as hereinbefore stated, the impact imparted to each coupler bythe other is the same, what has been stated above in regard to thestruck car equally applies to the draft gear apparatus provided on themoving car.

The pressures established in the bottom bores 28 and 29 in response tothe corresponding pistons 33 and 43 traveling respectively in thedirection of the left and right hand through their full length of strokeconstitutes a hydraulic head of oil for forcing the oil from therespective bottom bores 28 and 29 through the orifice formed between themetering rod 48 and the tapered bore 32 to the chambers 31 and 76.

The general equation for the velocity of spouting liquid is V= /2gH,where V=theoretical velocity in feet per second, g=acceleration ofgravity in feet per second per second, and H=head of liquid in feet. Thedischarge from an orifice in cubic feet per second is equal to theproduct of the actual velocity and the area of the jet. (The aboveequations are from section 5, page 09 of Power Volume, twelfth edition,Kents Mechanical Engineers Handbook.)

The total quantity of oil discharged from the orifice may be expressedby the equation Q 712, where n represents the discharge in cubic feetper second and t the time in seconds that the discharge through theorifice continues.

From the above equations, it is apparent that the total quantity of oildischarged from the bottom bores 28 and 29 through the orifice to thechambers 31 and 76 is dependent on the sum of the pressures in thebottom bores 28 and 29 and the sum of the length of time required forthe two pistons 33 and 43 to travel the respective full length of theirstrokes. The length of travel of a standard sliding sill used on freightcars today is approximately thirty inches. Also, it will be understoodthat the kinetic energy absorbed by a single piston draft gear deviceused with this standard sliding sill is a function of this length ofstroke. In the draft gear device 13 constituting the present inventionit is apparent that the time required for the discharge of oil throughthe orifice is dependent on the sum of the time required for the piston33 to complete the full length of its stroke, which length of stroke itwill be understood is the same as the length of travel of the slidingsill 21, and the time required for the piston 43 to complete the lengthof its stroke. Since the full length of stroke of the two pistons 33 and43 may be approximately the same, it is apparent that the kinetic energyabsorbing capacity of the draft gear device 13 for a chosen travel ofthe sliding sill 21 is approximately twice the kinetic energy absorbingcapacity of a single piston conventional draft gear device used with asliding sill having the same length of stroke as the sliding sill 21.From the above it may be seen that by the use of the draft gear device13 the length of stroke or travel of the sliding sill can be reduced onehalf and yet obtain the same cushioning protection for the lading orload carried by the freight car.

Freight cars using conventional sliding sill construction require, inaddition to the draft gear device operatively connected to the slidingsill and located approximately midway the length of the car, two otherdraft gear devices, one associated with each of the two car couplers. Itmay be noted, however, that by using a draft gear device 13 at each endof a freight car only two draft gear devices per car are requiredthereby reducing substantially the cost of providing adequate cushioningfor the lading carried in the body of the car.

The amount of kinetic energy absorbed may be expressed mathematically inmanner well known to those skilled in the art by use of the generalequation for kinetic energy:

nw m(at) E 2 T 2 Where m=mass=weight+g; v=velocity in feet per second;a=acceleration in feet per second per second; t: time in seconds.

Reference may be had to the American Society of Mechanical EngineersPaper No. 61WA256 covering The Design of Cushioning Gears for Rail-CarApplications by Robert L. Hassenauer and George E. Novak presented atthe Winter Annual Meeting in New York, N.Y., Nov. 26-Dec. 1, 1961, for afuller explanation of a method of calculating the relative accelerationbetween a rail car and its lading occurring as the result of a movingcar striking a stationary car or string of cars.

13 From the above-mentioned equation for kinetic energy lem it will beappreciated that where the sum of the length of stroke of the twopistons 33 and 43 is equal to the length of stroke of the piston of astandard draft gear device operatively connected to a sliding sillhaving twice the length of travel as the sliding sill 21, the timerequired for the oil to be forced from the bottom bores 28 and 29through the orifice provided between the periphery of the metering rod48 and the wall of the tapered bore 32 to the chambers 31 and 76 is thesame as the time required for the piston of the standard draft geardevice to force the oil through the orifice of this standard draft geardevice. Accordingly, it will be apparent that the kinetic energydissipated by flow of the oil through the orifice of the draft geardevice 13 associated with the sliding sill 21 is the same as the kineticenergy dissipated by a standard draft gear device associated with asliding sill having a length of travel twice the length of travel of thesliding sill 21. In other words, for the same cushioning effect, thedraft gear device 13 provides for reducing the travel of the slidingsill fifty percent.

When the velocity of the moving car and the velocity of the struck caror string of cars become the same, there is no further deceleration ofthe moving car, and, likewise, no further acceleration of the struck caror string of cars. Accordingly, in view of the above-mentioned generalequation for kinetic energy of mV T and the general equation for forceof F =ma, where F: force in pounds, mt=mass=weight divided by 32.174feet per second per second (acceleration due to gravity), anda=acceleration in feet per second per second, it is apparent that andthat if F/a be substituted for m in the above-mentioned general equationfor kinetic energy, it will be seen that From this equation for force,it will be seen that when a, the acceleration, becomes zero, the force Flikewise becomes Zero. Therefore, it is apparent that when the velocityof the moving car and the velocity of the struck car or cars become thesame, at which time there is no acceleration or deceleration of any ofthese cars, the impacting force acting on the piston rods 35 and 47 andthe corresponding pistons 33 and 43 is likewise zero, for if zero besubstituted for a in the equation the force F becomes zero.

One-half the weight of the car and its load is now acting in a downwarddirection on the piston 75 via the piston rod 84 and, therefore, iseffective to move the piston 75 downward to cause it to force oil toflow from the chamber 76 to the bottom bores 28 and 29 via nipple 78,hose 79, nipple 81, chamber 31, tapered bore 32 and passageway 30. Theoil thus supplied to the bottom bores 28 and 29 will cause therespective pistons 33 and 43 and their corresponding piston rods 35 and47 to be moved to the position in which they are shown in FIG. 1 or inother words to the original position these pistons and piston rodsoccupied prior to the moving car striking the standing car or string ofcars.

14 (b) Draft impact-car coupled in a train Let it be assumed that afreight car provided with a draft gear device 13 at each end is coupledin a train.

Now let it be supported that the train is standing and the engineerdesires to start the train. To do so, he moves the controller handlefrom idle position to a power position. This effects the supply of powerto the driving wheels of the locomotive to start the locomotive from astopped position. The initial movement of the locomotive is transmittedfrom the coupler at the train end of the locomotive to the coupler atthe locomotive end of the first car in the train. Accordingly, let it besupposed that the shank 6 shown in FIG. 1 of the drawings is the shankof the coupler at the locomotive end of the first car in the train.Therefore, the initial movement of the locomotive is effective to exerta pull or jerk and thereby establish a force that acts in the directionof the left hand on the shank 6 shown in FIG. 1. This force acting onthe shank 6 is transmitted through this shank to the shank pin 9. Sincethe shank pin 9 extends through the hereinbeforementioned elongatedslots in the opposite vertical side walls 2 and 3 (FIGS. 2 and 3) of thedraft gear yoke 4, the shank pin 9 is effective to transmit the forceexerted by the locomotive to the draft gear yoke 4. As shown in FIG. 1,the right-hand end wall of the draft gear yoke pocket 1 abuts theright-hand end of the casing 26 of the draft gear device 13. Therefore,the pull on the draft gear yoke 4 in the direction of the left hand, asviewed in FIG. 1, will be transmitted to the casing 26. Accordingly,upon movement of the draft gear yoke 4, the casing 26 is moved in thedirection of the left hand in response to the pull exerted in thisdirection by the locomotive on the shank 6 of the car coupler.

It will be noted that the upper and lower ends of the left-hand side ofthe follower 7 normally abut, respectively, the front draft gear lugs 66and 67 which, as hereinbefore stated, are secured to the fixed centersill 11 of the car. Likewise, it will be noted that the right-hand sideof the follower 7 abuts the left-hand end of the piston rod 47.Accordingly, it will be apparent that as the draft gear yoke 4 and thecasing 26 are moved in the direction of the left hand, the casing 26 ismoved with respect to the piston 43, piston rod 45 and metering rod 48to decrease the volume of the bottom bore 29 on the right-hand side ofthe; piston 43. As this movement of the yoke 4 and casing 26 continuesin the direction of the left hand, the piston 43 is effective to forcethe oil in the bottom bore 29 to flow at a relatively high velocitythrough the orifice formed between the periphery of the metering rod 48and the wall surface of the tapered bore 32, as this metering rod entersthis bore, to chambers 31 and 76 to respectively dissipate kineticenergy as heat and do work in moving the piston upward in the mannerhereinbefore explained.

Furthermore, the friction of the draft gear yoke 4 and other movingparts of the mechanism are effective to dissipate or absorb some of thiskinetic energy transmitted by the pull or jerk of the locomotive to theshank 6 of the car coupler. Therefore, all of the kinetic energyresulting from the jerk exerted on the shank 6 of the coupler on thatend of the first car adjacent the train end of the locomotive isdissipated (1) in the form of the work done by the piston 43 in forcingoil from the bottom bore 29 to the chamber 76 to lift one half theweight of the car body and the load carrier thereon, (2) in the form ofheat by the passing of the oil through the orifice, (3) the turbulencein the chamber 31, and (4) the friction of the various parts of thedraft gear mechanism, or is transferred via the oil in the casing 26 tothe piston 43 and thence to the fixed center sill 11 via the piston rod47, follower 7 and the front draft gear lugs 66 and 67. This remainingkinetic energy that is not absorbed by the hydraulic draft gearmechanism and friction but is transmitted to the fixed center sill 11 ofthe first car in the train is effective to move this center sill 11 andthe two trucks 0f the car to which it is connected from their standingposition in the same direction as the initial movement of thelocomotive.

The inertia of the car body and the load carried thereon resist movementfrom their state of rest. Since the car body and the load carriedthereon are supported on the sliding sill 21 which rests on the rollers59 which in turn are supported on the draft gear carrier 56 that issecured to the Z-sections 15 and 16 (FIG. 2) that constitute the fixedcenter sill 11, it will be apparent that as the fixed center sill 11 andthe two car trucks are moved in the direction of the left hand, asviewed in FIG. 1, by the tractive effort of the locomotive, the inertiaresistance of the car body and its load causes the car body, the loadtherein and the sliding sill 21, all of which are supported on theplurality of rollers 59, to move, as viewed in FIG. 1, in the directionof the right hand relative to the fixed center sill 11 which, it will beunderstood, is being pulled by the tractive effort of the locomotive inthe direction of the left hand. Stated in other Words, the inertiaresistance of the car body and the load carried thereon tends to preventmovement of the car body and sliding sill 21 simultaneously withmovement of the fixed center sill 11 and the two car trucks operativelyconnected thereto.

This inertia resistance of the car body and its load to movement in thedirection of the left hand simultaneously as the fixed center sill 11and the two car trucks are moved in the direction of the left hand bythe tractive effort of the locomotive, is effective to cause the slidingsill 21 to move in the direction of the right hand relative to the fixedcenter sill 11 and transmit a force to the piston 33 of the draft geardevice 13 at the right-hand end of the car via the corresponding bumperblock 64 and piston rod 35. The right-hand end of the casing 26 of thedraft gear device -13 at the right-hand end of the car rests against thefront draft gear lugs 66 and 67 at this end of the car so that thiscasing 26 is moved in the direction of the left hand as the fixed centersill 11 is moved in the direction of the left hand by the tractiveeffort of the locomotive. Since the sliding sill 21 with the car bodyand its load supported thereon, the piston rod and piston 33 are nowbeing moved in the direction of the right hand, as viewed in FIG. 1, andthe casing 26 of the draft gear device 13 at the right-hand end of thecar is now being moved in the direction of the left hand, it is apparentthat this piston 33 will force oil from the corresponding bottom bore 28to the chamber 76 of the load Weighing cylinder 72 carried by thebolster of the car truck at the right-hand end of the car in the mannerhereinbefore explained. This supply of oil to the chamber 76 iseffective on the lower face of the piston 75 to lift the right-hand endof the car against one half the weight of the car body and the loadthereon in the manner hereinbefore explained. Accordingly, it isapparent that the draft gear apparatus at the right-hand end of the carabsorbs kinetic energy by doing work in lifting the right-hand end ofthe car. Therefore, the total kinetic energy absorbed in draft is equalto the sum of the kinetic energy absorbed by the two draft gear deviceslocated at the respective opposite ends of the car. From the foregoing,it is apparent that for a given force applied to the shank 6 of the carcoupler, either in buff or in draft, the draft gear device or devices 13absorb the same amount of kinetic energy.

The operation of the draft gear devices associated with the car couplesat the adjacent ends of any two coupled cars in a train is the same asthe operation of the draft gear device associated with the coupler atthe train end of the locomotive and the draft gear device associatedwith the coupler at the locomotive end of the first car in the train.Therefore, a detailed description of the operation of the draft geardevices associated with the car couplers at the respective adjacent endsof two coupled cars is not deemed necessary.

Having now described the invention, what we claim as new and desire tosecure by Letters Patent is:

1. In a railway car having at least one truck bolster, a fixed centersill supported at one end on said bolster and provided with a fixedcenter sill pocket, and a carbody-carrying sliding sill movablysupported in straddling relation to the fixed center sill forlongitudinal movement with respect thereto, a hydraulic draft gearassembly comprising:

(a) a draft gear yoke movable in the fixed center sill pocket relativeto the fixedcenter sill responsively to draft and buff forces exertedthereon, said yoke having an elongated slot,

(b) a draft gear device disposed in said elongated slot and pocket andhaving two fluid motors, each of said fluid motors comprising a hollowcylinder and a piston slidably mounted therein for cooperation therewithto form a chamber containing hydraulic fluid, one of said fluid motorsbeing interposed between said yoke and the fixed center sill in such amanner that relative movement between the corresponding cylinder andpiston, caused by movement of said yoke relative to the fixed centersill in either direction, effects the displacement of hydraulic fluidfrom the corresponding chamber of said one fluid motor to cause theabsorption of an amount of energy corresponding to the amount ofmovement of the yoke relative to the fixed center sill and the other ofsaid fluid motors being interposed between said yoke and the slidingsill in such a manner that movement of the piston of said other fluidmotor relative to its corresponding cylinder, in response to movement ofthe sliding sill in one direction relative to the fixed center sill,effects the displacement of hydraulic fluid from the correspondingchamber of said other fluid motor to cause the absorption of anotheramount of energy corresponding to the amount of movement of the slidingsill in response to inertia forces acting thereon, and

(c) a third fluid motor comprising a hollow cylinder and a pistonslidably mounted therein for cooperation therewith to form adisplacement chamber containing hydraulic fluid and connected to thechambers of said two fluid motors, said third fluid motor being carriedby the truck bolster and supporting one end of the fixed center sillwhereby, upon displacement of hydraulic fluid from the chamber of eitheror both of said fluid motors to said displacement chamber, said thirdfluid motor is effective to absorb energy in lifting a portion of theload supported on the fixed center sill in response to the increase inpressure of hydraulic fluid effected in said displacement chamher.

2. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized in that said two fluid motors of said draft gear deviceare arranged one above the other with their longitudinal center lineslying in the same vertical plane, the longitudinal center line of thelower fluid motor coinciding substantially with the longitudinal centerline of the fixed center sill and the longitudinal center line of theupper fluid motor being disposed above the sliding sill and parallel tothe longitudinal center line thereof.

3. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized by a flow-restricting orifice through which hydraulicfluid is supplied from said two fluid motors to said displacementchamber.

4. A hydraulic draft gear assembly, as claimed in claim 3, furthercharacterized in that one of said two fluid motors is provided with atapered metering pin which, upon operation of said one fluid motor inresponse to buff or draft forces is moved into said orifice to effect adecrease in the effective area of said orifice, thereby to regulate theforce on said draft gear yoke.

5 In a railway car having a pair of truck bolsters one at each endthereof, a fixed center sill supported at its respective opposite endson said truck bolsters and provided with a center sill pocket, and acar-body-carrying sliding sill movably supported in straddling relationto the fixed center sill for longitudinal movement with respect thereto,the combination of a pair of hydraulic draft gear assemblies, one at oneend of the car and the other at the opposite end of the car, each draftgear assembly comprising:

(a) a draft gear yoke movable in the fixed center sill pocket relativeto the fixed center sill responsively to draft and buff forces exertedthereon, said yoke having an elongated slot,

(b) a draft gear device disposed in said elongated slot and pocket andhaving two fluid motors, each of said fluid motors comprising a hollowcylinder and a piston slidably mounted therein for cooperation therewithto form a chamber containing hydraulic fluid, one of said fluid motorsbeing interposed between said yoke and the fixed center sill in such amanner that relative movement between the corresponding cylinder andpiston by movement of said yoke relative to the fixed center sill ineither direction, effects the displacement of hydraulic fluid from thecorresponding chamber of said one fluid motor in response to theapplication of a draft or buff force to said yoke to cause theabsorption of an amount of energy corresponding to the amount ofmovement of the yoke relative to the fixed center sill and the other ofsaid fluid motors being interposed between said yoke and the slidingsill in such a manner that movement of the piston of said other fluidmotor relative to its corresponding cylinder in response to movement ofthe sliding sill in one direction relative to the fixed center sill byinertia forces acting on the sliding sill resulting from only theapplication of a buff force to said yoke causes the absorption ofanother amount of energy corre sponding to the amount of movement of thesliding center sill, and

(c) a third fluid motor comprising a hollow cylinder and a pistonslidably mounted therein for cooperation therewith to form adisplacement chamber connected to the chambers of said two fluid motorsof the draft gear device at the corresponding end of the car, said thirdfluid motor being carried by the truck bolster at said corresponding endand supporting the corresponding end of the fixed center sill whereby,upon displacement of hydraulic fluid from the chamber of either or bothof said two fluid motors at said corresponding end to said displacementchamber, said third fluid motor is effective to absorb energy in liftinga portion of the load supported on the fixed center sill in response tothe increase in pressure of hydraulic fluid efiected in saidcorresponding displacement chamber,

(d) the other of said fluid motors of the draft gear device at theopposite end of the car cooperating with the fixed center sill onmovement of the sliding sill in the direction opposite said onedirection relative to the fixed center sill resulting from theapplication of a draft force to the yoke at the one end of the car tocause the absorption of said another amount of energy concurrently withabsorption of energy by said one fluid motor of the draft gear device atsaid one end of the car.

6. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized in that said draft gear device is slidably supported onthe fixed center sill for limited longitudinal movement within saidfixed center sill pocket.

7. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized in that said third fluid motor comprises a piston rod, andin that the fixed center sill is provided with a king pin that isreceived in said piston rod of said third fluid motor to thereby providefor 18 angular movement between the fixed center sill and the truckbolster.

8. A hydraulic draft gear assembly as claimed in claim 1, furthercharacterized by a flexible conduit via which hydraulic fluid issupplied from said two fluid motors of said draft gear device to saidbolster-supported third fluid motor to maintain fluid communicationbetween said two fluid motors and said third fluid motor notwithstandingrelative angular movement between the fixed center sill and the bolster.

9. A hydraulic draft gear assembly, as claimed in claim 7, furthercharacterized in that the connection between the chambers of said twofluid motors of said draft gear device and said displacement chamber ofsaid third fluid motor constitutes a hydraulic link and in that uponflow of hydraulic fluid from one or both of the chambers of said twofluid motors to said displacement chamber of said third fluid motor, inresponse to actuation of said one or both of said two fluid motors inresponse to a force acting thereon, said piston and piston rod transmita lifting force to the fixed center sill whereby it is moved verticallyupward until the work done in lifting the said fixed center sill isequal to the work done by said one or both of said two fluid motors inforcing fluid therefrom through said hydraulic link to said third fluidmotor.

10. A hydraulic draft gear assembly, as claimed in claim 7, furthercharacterized in that the force transmitted to the fixed center sill bythe piston and piston rod of said third fluid motor is resisted by agravitational force that acts in the opposite direction and is of amagnitude proportional to the load carried on the fixed center sill.

11. A hydraulic draft gear assembly, as claimed in claim 2, furthercharacterized in that upon application of a buff force to one fluidmotor of the draft gear device, the other fluid motor of the draft geardevice is subject to an inertia force proportional to the weight of theload carried on the sliding sill.

12. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized in that for each increment of increase of travel of saidpistons of said two fluid motors, the energy absorbing capacity of saiddraft gear device is increased proportionally to the summation of theincrement of increase of travel of said pistons.

13. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized in that both of said fluid motors of said draft geardevice are operative to cause the absorption of the kinetic energy ofimpact of two colliding railway cars in response to the application of abuff force to the corresponding draft gear yoke, and in that only one ofsaid fluid motors of said draft gear device is operative to cause theabsorption of kinetic energy resulting from the application of a draftforce to the corresponding draft gear yoke.

14. A hydraulic draft gear assembly, as claimed in claim 1, furthercharacterized in that the pressure chamber of said one fluid motor andthat of said other fluid motor are connected 'without restriction, andin that the pressure chamber of said one fluid motor communicates withthe pressure chamber of said third fluid motor via a flow-restrictingorifice, the piston of said one fluid motor having thereon a meteringrod in coaxial alignment with said orifice and which is moved into saidorifice upon relative movement between the piston of said one fluidmotor and its corresponding cylinder in response to buff or draft forcesto reduce flow from the pressure chambers of said one and said otherfluid motors to the displacement chamber of said third fluid motor.

References Cited UNITED STATES PATENTS 3,259,252 7/1966 Peterson 21343DRAYTON E. HOFFMAN, Primary Examiner.

U.S. Cl. XJR. -454; 213-43

